A chemically modified soy protein gel was prepared by first preheating and then acylating the soy protein with ethylenediaminetetraacetic dianhydride (EDTAD)

followed by crosslinking with glutaraldehyde.The variation of molecular structure of modified soy protein and the variation of swelling ratio of gels were investigated; moreover

the swelling behavior of modified soy protein gels at different mEDTAD:mSPI and different pH was analyzed by treating the swelling data with mathematical method.The results showed that the free amimo groups of soy protein side chain reacted with EDTAD

which incorporated carboxyl groups into soy protein molecule chain; the ratio of the amount of added carboxyl group and lost amino group was about 3∶1 in soy protein molecules.The swelling ratio of soy protein-based gels was 24.2

54.07

87.27 and 95.87 when mEDTAD:mSPI was 0

0.05

0.1 and 0.2

respectively

which showed that increasing the amount of EDTAD incoporating into the protein molecular chain resulted in the increasing of swelling ratio of gels.The swelling characteristic exponent (n) of the above gels was about 0.5

which meant that the protein-based gels appeared Fickian’s diffusion behavior in water

the same behavior appeared to the modified soy protein gels at pH 10.04; but at pH 4.30 and pH 6.08

the range of n was 0.5 n 1

which meant a non-Fickian’s diffusion behavior.The mechanism of swelling behavior of gels was discussed.The swelling ratio of gels appeared pH-sensitivity

the “W”— shaped curve of swelling — deswelling process appeared

which meant the function of “shape memory” of gels.